Vacuum appliances capable of picking up both wet and dry material, commonly referred to as wet/dry vacuums or wet/dry vacs, are well-known. Wet/dry vacs are often used in workshops and other environments where both wet and dry debris can accumulate.
Wet/dry vacs conventionally consist of a collection tank or canister, sometimes mounted on wheels or casters, and a cover or lid upon which a motor and impeller assembly is mounted. The motor and impeller assembly creates a suction within the canister, such that debris and liquid are drawn in to the canister through an air inlet to which a flexible hose can be attached. A filter within the canister prevents incoming debris from escaping from the canister while allowing filtered air to escape. One example of a such a wet/dry vac is shown in U.S. Pat. No. 4,797,072.
Wet/dry vacs are commercially available in a variety of sizes and configurations. The capacity, i.e., size, of a wet/dry vacuum collection canister, is typically measured in gallons. In many cases, the vacuum collection canister has a round or cylindrical configuration, since such a configuration represents the stablest pressure vessel, capable of withstanding the negative pressure (vacuum) forces that can be generated within a wet/dry vac.
While larger capacity wet/dry vacs tend to be more powerful and are able to pick up more debris before needing to be emptied, they also tend to be heavier and more awkward. Maneuvering a large, e.g., 12- to 16-gallon wet/dry vac in small or cluttered areas can be difficult. Additionally, since the motor of a wet/dry vac is typically disposed on top of the canister, wet/dry vacs tend to have a high center of gravity, making them prone to tipping over. This problem, recognized for example in U.S. Pat. No. 5,560,075 to Jankowski entitled "Wet or Dry Vacuum With Low Center of Gravity," tends to worsen as the capacity of the vac increases.